This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall objective of this proposal is to take an advantage of two dimensional ultrasound phased arrays for image guided thermal ablation. Two dimensional phased arrays offer several advantages over single focused transducers. First, in an array, the location of the focus is controlled by an electronic signal so it is not necessary to physically move the applicator with a mechanical positioning device to shift the focal location. This ability allows fast focusing, making it possible to track moving targets. It also minimizes the space requirements for the sonication system and allows one to rapidly move the focus and to generate multiple foci simultaneously. Second, the shape of the ultrasound field is controlled by the driving signals, thus allowing departure from a sharp, elongated focus. This feature makes it possible to enlarge the coagulated volume per sonication and to optimize the focal shape for each treatment and even for each sonication during a treatment. Finally, with a phased array applicator, distortions to the ultrasound wave induced by the overlying tissues can be compensated for using imaging information of the wave propagation path.